Patent Literatures 1 and 2 disclose heat exchangers. Hereinafter, the heat exchangers described in Patent Literatures 1 and 2 will be briefly explained with the reference signs used in Patent Literatures 1 and 2 being given in parentheses.
In the heat exchanger described in Patent Literature 1, flat rectangular-tubular tubes (110) are stacked, and gas passes through inside the tubes (110). Protruding portions (112) are formed at outer edges of a bonding surface of the tube (110), and the protruding portions (112) of the tubes (110) adjacent to each other are joined together such that a flow path (115) surrounded with the protruding portions (112) is formed between the adjacent tubes (110). The protruding portions (112) are not formed in four portions (113a, 113b) in the outer edges of the bonding surface of the tube (110), and these portions (113a, 113b) form opening portions in which two opening portions (113a) serve as entrances to the flow path (115) and the other two opening portions (113b) serve as exits from the flow path (115). The stacked body of the tubes (110) is housed in a tubular water tank (130), and the tubular water tank (130) bulges out around the opening portions (113a) serving as the entrances. A pipe hole (132d) is formed in a part facing the opening portions (113a) of a bulging portion (132b), and cooling water is introduced into the bulging portion (132b) through the pipe hole (132b). Accordingly, the cooling water flows from the bulging portion (132b) to the flow paths (115) through the opening portions (113a).
In the heat exchanger described in Patent Literature 2, flat rectangular-tubular tubes (110) are stacked, and gas passes through inside the tubes (110). Protruding portions (112) are formed at outer edges of a bonding surface of the tube (110), and the protruding portions (112) of tubes (110) adjacent to each other are joined together such that a flow path (113) surrounded by the protruding portions (112) is formed between the adjacent tubes (110). The protruding portions (112) are not formed in two portions (113a, 113b) in the outer edges of the bonding surface of the tube (110), and these portions (113a, 113b) form opening portions in which one opening portion (113a) serves as an entrance to the flow path (113) and the other opening portion (113b) serves as an exit from the flow path (113). The stacked body of the tubes (110) is housed in a tubular water tank (130). An end portion of the stacked body of the tubes (110) is fitted in an opening portion (146) of an inner gas tank (140B), and an outer peripheral surface of the end portion is joined to an inner peripheral surface of the opening portion (146) of the inner gas tank (140B). This allows gas introduced into the inner gas tank (140B) to flow into the tubes (110). The inner gas tank (140B) is housed in an outer tank (140A), and cooling water is introduced into the outer tank (140A). A joint part at which the stacked body of the tubes (110) and the inner gas tank (140B) are joined together is arranged in an opening of the outer tank (140A). The opening of the outer tank (140A) is connected with an opening of the tubular water tank (130). For the cooling water introduced into the outer tank (140A), a flow path (150) is formed between the outer surfaces of the inner gas tank (140B) and the stacked body of the tubes (110) and the inner surfaces of the outer tank (140) and the tubular water tank (130), and the cooling water introduced into the outer tank (140A) flows into the above-described opening portions (113a) through the flow path (150). Accordingly, the cooling water flows into the flow paths (113) each between the tubes (110) adjacent to each other.